Field of the Invention
The present invention relates to a touch sensor-integrated type display device and, more particularly, to a touch sensor-integrated type display device capable of improving touch precision in a corner or edge portion and also achieving a narrow bezel.
Discussion of the Related Art
Recently, various input devices, such as keyboards, mouses, track balls, joysticks, and digitizers, are used to form an interface between a user and home appliances or various information communication devices. It is difficult to increase the completeness of a product because how to use such input devices needs to be known in order to use the input devices and inconvenience is caused due to some space occupied by the input devices. Accordingly, there is an increasing need for an input device which is convenient and simple and can reduce a malfunction. In line with such a need, there has been proposed a touch sensor in which a user inputs information by directly touching a screen with a finger or pen or by bringing a finger or pen to a screen while viewing the display devices of home appliances or various information communication devices.
The touch sensor is applied to various display devices because the touch sensor is simple and has less malfunctions and enables input even without using a separate input device and a user can manipulate the touch sensor rapidly and easily through contents displayed on a screen.
The touch sensor may be classified into an add-on type, an on-cell type, and an integrated type (or in-cell type) depending on its structure. The add-on type is a method of individually fabricating a touch panel in which a display device and a touch sensor have been formed and attaching a touch panel to the upper plate of the display device. The on-cell type is a method of directly forming a touch sensor on a surface of the upper glass substrate of a display device. The integrated type is a method capable of achieving the thinness of a display device and improving durability by embedding a touch sensor in a display device.
The add-on type touch sensor has a structure in which a completed touch panel is mounted on a display device and is problematic in that it has a thick thickness and has low visibility because brightness of a display device is low.
The on-cell type touch sensor has a structure in which a separate touch sensor is formed on the top surface of a display device. The on-cell type touch sensor has a thinner thickness than the add-on type touch sensor, but is problematic in that a total thickness is increased due to a driving electrode layer forming a touch sensor, a sensing electrode layer, and an insulating layer for insulating the driving electrode layer and the sensing electrode layer.
The integrated type touch sensor has been in the spotlight because it can solve the disadvantages of the add-on type touch sensor and the on-cell type touch sensor in that durability and thinness can be obtained. The integrated type touch sensor is classified into an optical type and a capacitance type depending on a method of sensing a touched portion. The capacitance type is classified into a self-capacitance type and a mutual capacitance type.
The self-capacitance type touch sensor adopts a method of forming a plurality of independent patterns in the touch region of a touch sense panel and determining whether a touch is present by measuring a change of capacitance in each independent pattern.
The mutual capacitance type touch sensor adopts a method of forming a matrix by intersecting X-axis electrode lines (e.g., driving electrode lines) and Y-axis electrode lines (e.g., sensing electrode lines) in the touch electrode forming region of a touch sense panel, applying a driving pulse to the X-axis electrode lines, and determining whether a touch is present by sensing a change of a voltage in sensing nodes defined as the crossing of the X-axis electrode lines and the Y-axis electrode lines through the Y-axis electrode lines.
A related art touch sensor-integrated type liquid crystal display device of a self-capacitance type is described below with reference to FIG. 1. FIG. 1 is a schematic plan view showing a related art touch sensor-integrated type liquid crystal display device of a self-capacitance type.
Referring to FIG. 1, the touch sensor-integrated type display device of a self-capacitance type includes an active area AA in which touch electrodes are formed and data is displayed and a bezel area BA disposed on the outside of the active area AA. Various lines, a source driving and touch sensing integrated chip (IC) 10 in which ICs for source driver and ICs for touch controller have been integrated, and an IC 20 for gate driver are formed in the bezel area BA.
The active area AA includes a plurality of touch electrodes Tx11˜Tx1m, Tx21˜Tx2m, Tx31˜Tx3m, . . . , Txn1˜Txnm arranged in a first direction (e.g., X-axis direction) and a second direction (e.g., Y-axis direction) which cross each other and a plurality of routing lines TW11˜TW1n, TW21˜TW2n, TW31˜TW3n, . . . , TWn1˜TWnm respectively connected to the plurality of touch electrodes Tx11˜Tx1m, Tx21˜Tx2m, Tx31˜Tx3m, . . . , Txn1˜Txnm and arranged in parallel in the second direction.
The plurality of touch electrodes Tx11˜Tx1m, Tx21˜Tx2m, Tx31˜Tx3m, . . . , Txn1˜Txnm formed in the active area AA are formed by dividing a common electrode of the display device. The touch electrodes operate as the common electrode during a display operation for displaying data and operate as touch electrodes during a touch operation for recognizing touch locations.
The bezel area BA is disposed on the outside of the active area AA and includes the source driving and touch sensing IC 10, the gate driver 20, and various lines. During the touch operation, the source driving and touch sensing IC 10 supplies display data to data lines of the display device depending on driving of gate lines. During the touch operation, the source driving and touch sensing IC 10 supplies a touch driving voltage to the touch electrodes Tx11˜Tx1m, Tx21˜Tx2m, Tx31˜Tx3m, . . . , Txn1˜Txnm and determines the location of touch electrodes on which a touch has been performed by scanning changes of capacitance of the touch electrodes before and after the touch. The various lines include the routing lines TW11˜TW1n, TW21˜TW2n, TW31˜TW3n, . . . , TWm1˜TWmn connected to the touch electrodes Tx11˜Tx1m, Tx21˜Tx2m, Tx31˜Tx3m, . . . , Txn1˜Txnm, the data lines connected to the source driving and touch sensing IC 10, and the gate lines connected to the gate driver 20.
In the aforementioned touch sensor-integrated type display device of a self-capacitance type, when a finger or conductive metal, such as a stylus pen, touches the active area AA of the display device, the source driving and touch sensing IC 10 may detect touch locations by recognizing changes of capacitance in the touch electrodes before and after a touch event. That is, the source driving and touch sensing IC 10 may apply a driving pulse to the touch electrodes Tx11˜Tx1m, Tx21˜Tx2m, Tx31˜Tx3m, . . . , Txn1˜Txnm formed in the active area AA and may detect a touch location by sensing the touch electrodes Tx11˜Tx1m, Tx21˜Tx2m, Tx31˜Tx3m, . . . , Txn1˜Txnm by measuring a change of self-capacitance in each of the touch electrodes before and after the touch event.
The accuracy of touch sensitivity according to a touch location is described below with reference to FIG. 2. FIG. 2 is a plan view showing a touch location in the related art touch sensor-integrated type display device in order to describe the accuracy of touch sensitivity.
The amount of capacitance changed according to each of touch locations “a” to “d” is described with reference to FIG. 2. Each of the touch electrodes Tx11˜Tx1m, Tx21˜Tx2m, Tx31˜Tx3m, . . . , Txn1˜Txnm needs to be formed in a very small size because it has to accurately detect a touch location according to a finger or a stylus pen. Accordingly, when a touch is performed on the touch sensor-integrated type display device, only a single touch electrode is not touched, but an adjacent touch electrode(s) may be also touched.
Furthermore, touch sensitivity is increased in proportion to an area touched when a finger or a stylus pen touches the touch electrodes. Accordingly, touch sensitivity is more reduced when a touch is performed at the edge or corner of the active area AA than when a touch is performed within the active area AA.
For example, when four touch electrodes Tx22, Tx23, Tx32, and Tx33 are touched at the touch location “a” within the active area AA of FIG. 2 by a touch event, the amount of capacitance changed about each of the four touch electrodes Tx22, Tx23, Tx32, and Tx33 is accumulated and measured. Accordingly, an accurate touch location can be detected because the amount of changed capacitance is accumulated and calculated based on the area of the four touch electrodes Tx22, Tx23, Tx32, and Tx33.
In contrast, when a touch is performed at the corner of the active area AA of FIG. 2, that is, at the touch location “b” or “c”, only two touch electrodes Tx21 and Tx31 or Tx11 and Tx12 may be touched. In this case, the amount of capacitance changed about each of the two touch electrodes Tx21 and Tx31 or Tx11 and Tx12 is accumulated and measured. Accordingly, touch sensitivity is reduced compared to the touch location “a” because the amount of the changed capacitance is accumulated and calculated based on the area of the two touch electrodes Tx21 and Tx31 or Tx11 and Tx12.
Furthermore, when a touch is performed in the corner of the active area AA of FIG. 2, that is, at the touch location “d”, only the one touch electrode Tx11 may be touched. In this case, the amount of the changed capacitance about the one touch electrode Tx11 is measured. Accordingly, touch sensitivity is reduced compared to the touch location “b” or the touch location “c” because the amount of the changed capacitance is calculated based on the area of one touch electrode Tx in the corner part.
As described above, the amount of the changed capacitance is reduced as a touch position is moving toward the edge area or corner area of the active area AA because the amount of capacitance according to the touch location is different. Accordingly, there is a need for a solution capable of preventing a reduction of touch accuracy and linearity in the edge area and corner area of an active area.